Manchin knows that ending the filibuster is a bad idea, because it makes major change way too easy. Deep down Biden knows this too. Same with packing the courts. Both are institutionalists. Changing the rules to fill vacancies was important since those positions are to be filled. They weren't meant to be partisan obstruction. However, changing the rules to pass legislation is a really bad idea. It allows for major legislation to be easily passed and easily overturned. I wouldn't mind if there was a constitutional amendment requiring 60 votes in the Senate for legislation.